Hi my dad is still using his 2007 4cyl sonata and its been few days that when you want to start the car the in morning it starts ok but then idles rough and shuts off and you have pit push the gas pedal aswell right right after starting to make it run and not shutoff. Plus some black smokes comes put exhaust aswell after cols start. But after the cold start the car has no problem and idles and works fine. Its only the first cold start in the morning. What could be wrong ?